Kinetic analysis of 3beta-hydroxysteroid dehydrogenase in microsomes from complete hydatidiform mole

GENTI DE RAIMONDI SUSANA; OLIVIER NORA; PATRITO LUIS; FLURY ALFREDO

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1990 vol. 36 p. 149 - 149

ummary-Microsomes isolated from complete hydatidiform moles (CHM) were able to convert [?Hlpregnenolone to [3H]progesterone which indicates the presence of 3fl-hydroxysteroid dehydrogenase/isomerase (3fl-HSD) activity. The kinetic parameters found (K,,,= 0.63pM and V,,,,,,= l-3.05 nmol/min/mg of protein) were like those observed in microsomes from normal early placenta (NEP) of similar gestational age (herein) and term placenta [l] suggesting that the enzymes from the three sources are kinetically similar. Testosterone, progesterone and estradiol in a dose range of 0.05-5 pmol/l inhibited differently the in vitro conversion of [3H]pregnenolone to [3H]progesterone in a dose-dependent manner. The steroid concentrations necessary to inhibit the conversion of pregnenolone to progesterone by 50% (ID,,) in CHM were 0.1 PM for testosterone, 0.6 PM for progesterone and 3 pM for estradiol, whereas in NEP they were 2.5, 1 and 5 PM respectively. The Ki values calculated from these ID,